Turntables are commonly used on productions lines of various types in order to, for example, allow different tasks to be performed on related items within a given space. For example, a turntable could be used to allow workers to hand fill a empty rack at one station of a turntable, while a fork lift is used at a second station on the turntable to remove filled racks, and replace them with empty racks. As such, the worker is kept safely away from the fork lift, and can be actively filling a rack while the fork lift is occupied with removal of the filled rack, or the like. Once an empty rack has been filled, the turntable would be turned 180°, for a two-station turntable, so that the workers are presented with a new empty rack, and the fork lift would have easy access to remove the filled rack and replace it with an empty rack.
Turntables are used in a variety of applications, and can be of a variety of different sizes. The number of stations on the turntable can vary but is typically 4 or less. After each loading or unloading cycle, for example, is complete, the turntable would be turned an appropriate amount, in order to move the work product to the next station.
Turntables can be of any suitable size depending on the part size, and depending on the operation to be preformed. In some automotive applications, the size of the turntable can be relatively large. For example, a two station automotive turntable can be over 5 meters in diameter, while a three station automotive turntable can be over 7 meters in diameter. These devices are commonly made of steel in order to support the weight of the work product and, as such, rotation of the turntable can made difficult by the weight of the work product and the weight of the turntable itself.
Commonly, the turntable is supported by a series of rollers or the like under the turntable “floor” structure, and the turntable is turned using a motorized, belt or chain-driven connection to a gear structure which acts on the outer edge of the turntable. This arrangement can lead to wear and/or adjustment difficulties with the drive system and can lead to control problems as the turntable is rotated. Also, motorized, frictional drive systems are known where a drive wheel presses against the turntable, but these suffer from the constant need for adjustment of the frictional drive.
Drive systems are also known which use a horizontal motor located at or near the centre of the turntable structure but which are located on the floor or other support structure so as to be stationary, and connect to the central opening of an annular turntable using a frictional connection, or by using a pinion gear connected to a gear structure located on the inner annular surface of the turntable. However, in these devices, the motor and gear structure requires a significant amount of space and thus reduces the amount of space available for use on the turntable. Further, the gear structure is typically exposed and it is possible to inadvertently damage the gear structure.
Commonly, the floor of the turntable is round in overall shape, but is typically made of a collection of square plates which have been cut for this purpose. As such, the individual floor plates may be different from each other, and it can be difficult to fit the floor plates together in an apparent seamless configuration, particularly after installation and during use of the turntable structure. This is particularly true as the turntable is rotated and the support structure acts on different turntable plates. As such, the floor of the turntable may be uneven, and may contain vertical or horizontal gaps, or non-level sections which can make walking or movement of equipment on the turntable, difficult or unsafe. This is a particularly significant disadvantage in automated operations wherein “robotic” or other such devices travel across the turntable surface and the uneven floor can interfere with the movement of these robotic devices.
To overcome these difficulties, it would be advantageous to provide a turntable suitable for larger applications which provides a better support arrangement, allows for a common floor plate structure, avoids the difficulties of chain-driven, belt or frictional movement mechanisms, and facilitates the provision of a level floor structure in order to avoid vertical or horizontal gaps in the floor.